FAQ
TL;DR: ±2 ppm DS3231 keeps a Nixie clock within ±0.17 s/day, and “It works perfectly for almost a year” [Elektroda, Limonit, post #19331858] Modular design lets you swap displays, MCUs and sync sources in minutes. Why it matters: You can build or service an Open-Nixie without guessing specs.
Quick Facts
• Supply: 10–12 V DC input, 170–190 V boost for tubes [Elektroda, pawelr98, post #19335962]
• Display drive: 4× LC-513 or Z566M tubes via 74141 + MMBTA42/92 pairs [Elektroda, Limonit, post #19324601]
• Brightness: 50 % PWM, 200 µs period; refresh every 100 µs [Elektroda, Limonit, post #19324897]
• Timekeeping: DS3231 ±2 ppm, half-hour CPU sync [Elektroda, Limonit, post #19324897]
• Backup: CR1220 cell ≈ 3–5 years typical [Elektroda, Limonit, post #19325419]
How does the Open-Nixie measure and correct time?
The ATmega328 counts seconds with its internal timer, then resynchronises every 30 minutes to a DS3231 RTC. During each sync it trims timer-0 range to cancel RC-oscillator drift [Elektroda, Limonit, post #19324897]
Why not read the RTC each second instead of every 30 minutes?
Frequent I²C reads risk timing glitches if power drops mid-transfer, causing the RTC to jump to random dates [Elektroda, Limonit, post #19331858] Half-hour polling lowers that risk while using little CPU time.
Can I switch to continuous RTC reading anyway?
Yes. Continuous reads add <1 % CPU load and give ±2 ppm accuracy, provided your firmware manages I²C errors [Judas, #19330946].
Is display brightness adjustable?
Yes. A one-step dimmer imposes 50 % PWM on the multiplex signal; with LEDs off, it halves tube current without colour shift [Elektroda, Limonit, post #19324897]
Does PWM make the tubes audible at night?
Some users hear a faint 16–22 kHz “chirp” from electrode vibration during multiplex. Tweaking the sweep frequency 2–3 kHz higher usually silences it [Elektroda, Limonit, post #19582874]
Which boost-converter IC is best?
The stock MC34063 works but wastes power. A UC3843 includes a MOSFET driver, needs a smaller sense resistor and raises efficiency by ≈7 % [Elektroda, pawelr98, post #19335962]
How long will the backup battery last?
A CR1220 (38 mAh) powers the DS3231 for roughly 3–5 years at 2 µA load [Elektroda, Limonit, post #19325419]
Can I add radio (DCF77) synchronisation?
Possible but tricky. The HV converter floods the 77.5 kHz band, and receivers plus loop antennas rarely fit the Electronix case [Elektroda, Limonit, post #19331858]
What’s the alternative to DCF77?
Plug in a Wemos D1 mini logic board; Wi-Fi NTP sync every hour autocalibrates time with no cabling [Elektroda, Limonit, post #19332664]
Is there a risk of total time loss?
Edge case: an abrupt power cut during I²C transfer can corrupt RTC registers, forcing a manual reset [Elektroda, Limonit, post #19331858]
How do I retune PWM to stop audible noise?
- Open firmware and locate displayTimer ISR. 2. Change the refresh period until the tone disappears. 3. Re-flash MCU and test in a quiet room.
Where can I buy the acrylic case?
Search online for “electroNIXclock housing”—it is the same plexi enclosure used here [Elektroda, lombard1, post #19325377]
